4-(4-{[2-(4-chlorophenyl)-4,4-dimethylcyclohex-1-en-1-yl]methyl}piperazin-1-yl)-N-({3-nitro-4-[(tetrahydro-2H-pyran-4-ylmethyl)amino]phenyl}sulfonyl)-2-(1H-pyrrolo[2,3-b]pyridin-5-yloxy)benzamide (hereafter, “Compound 1”) is a potent and selective Bcl-2 inhibitor having, inter alia, antitumor activity as an apoptosis-inducing agent. Compound 1 has the formula:

Compound 1 is currently the subject of ongoing clinical trials for the treatment of chronic lymphocytic leukemia. U.S. Patent Publication No. 2010/0305122 describes Compound 1, and other compounds which exhibit potent binding to a Bcl-2 family protein, and pharmaceutically acceptable salts thereof. U.S. Patent Publication Nos. 2012/0108590 and 2012/0277210 describe pharmaceutical compositions comprising such compounds, and methods for the treatment of neoplastic, immune or autoimmune diseases comprising these compounds. U.S. Patent Publication No. 2012/0157470 describes pharmaceutically acceptable salts and crystalline forms of Compound 1. The disclosures of U.S. 2010/0305122; 2012/0108590; 2012/0157470 and 2012/0277210 are hereby incorporated by reference in their entireties.